Human Blood Meals in Sylvatic Triatomines Challenges Domestic-Centered Strategies for Prevention of Trypanosoma cruzi Transmission in Ecuador.

Transmission risk of Chagas disease has been associated with human-vector contacts and triatomines colonizing dwellings, but alternative scenarios, independent of domestic colonization, are poorly documented. In the present work, we estimated the frequency of human blood meals in triatomines from domicile, peridomicile, and sylvatic environments in two endemic regions in Ecuador. Blood meal origins were identified by sequencing a cytb gene fragment. Human blood meals were detected in 42% of the triatomines among 416 analyzed, including 48% of sylvatic triatomines (both adults and nymphs). In triatomines from domicile and peridomicile, Trypanosoma cruzi infection rate was > 20%, and reached 48% in sylvatic triatomines. Human is a common source of blood for triatomines whether they live in or near dwellings in both regions, and the high rate of T. cruzi infection represents an important risk of transmission of Chagas disease. Consequently, control strategies should also take into account possible nondomestic transmission.

Tolerance to Trypanosomatids: A Threat, or a Key for Disease Elimination?

So far, research on trypanosomatid infections has been driven by 'disease by disease' approaches, leading to different concepts and control strategies. It is, however, increasingly clear that they share common features such as the ability to generate long-lasting asymptomatic infections in their mammalian hosts. Trypanotolerance, long integrated in animal African trypanosomiasis control, historically refers to the ability of cattle breeds to limit Trypanosoma infection and pathology, but has only recently been recognized in humans. Whilst trypanotolerance is absent from the vocabulary on leishmaniasis and Chagas disease, asymptomatic infections also occur. We review the concept of trypanotolerance across the trypanosomatids and discuss the importance of asymptomatic carriage in the current context of elimination.

An experimental approach for the identification of conserved secreted proteins in trypanosomatids.

Extracellular factors produced by Leishmania spp., Trypanosoma cruzi, and Trypanosoma brucei are important in the host-parasite relationship. Here, we describe a genome-based approach to identify putative extracellular proteins conserved among trypanosomatids that are likely involved in the classical secretory pathway. Potentially secreted proteins were identified by bioinformatic analysis of the T. cruzi genome. A subset of thirteen genes encoding unknown proteins with orthologs containing a signal peptide sequence in L. infantum, L. major, and T. brucei were transfected into L. infantum. Tagged proteins detected in the extracellular medium confirmed computer predictions in about 25% of the hits. Secretion was confirmed for two L. infantum orthologs proteins using the same experimental system. Infectivity studies of transgenic Leishmania parasites suggest that one of the secreted proteins increases parasite replication inside macrophages. This methodology can identify conserved secreted proteins involved in the classical secretory pathway, and they may represent potential virulence factors in trypanosomatids.

Congenital Chagas disease involves Trypanosoma cruzi sub-lineage IId in the northwestern province of Salta, Argentina.

Trypanosoma cruzi is genetically classified into six discrete phylogenetic lineages on the basis of different genetic markers. Identifying lineages circulating among humans in different areas is essential to understand the molecular epidemiology of Chagas disease. In the present study, 18 T. cruzi isolates from congenitally infected newborns in the northwestern province of Salta-Argentina were studied by multilocus enzyme electrophoresis (MLEE) and random amplified polymorphic DNA (RAPD). All isolates were typed by MLEE and RAPD as belonging to T. cruzi IId. Analysis of minor variants of TcIId using probes hybridizing with hypervariable domains of kDNA minicircles, detected three variants with a similar distribution among the isolates. Our findings confirm the presence of T. cruzi IId among congenitally infected newborns in northwestern Argentina and support the assumption that human infection by T. cruzi in the Southern Cone countries of Latin America is due principally to T. cruzi II.

Peridomicilary habitat and risk factors for Triatoma infestation in a rural community of the Mexican occident.

An examination of peridomestic area organization and triatomine collection in an endemic village for Chagas disease (Jalisco State) identified the habitat of Triatoma longipennis (dominant species) and the risk factors of peridomestic infestation. In 100 visited peridomestic areas, 369 structures (permanent, temporary, and natural) were submitted to active manual research of triatomines. Storage shelters had a higher infestation of T. longipennis than piles of brick and tile; baked clay material had higher degrees of infestation than others. The secondary species Triatoma barberi shares a wide range of peridomicilary habitats with T. longipennis. Peridomestic area infestation risks (evaluated with multivariate logistic regression analysis) are number of closed storage shelters, number of brick and tile piles, number of houses per peridomestic areas, and distance of peridomicile from natural environment. Because both species present great adaptability to different artificial habitats, strategies of control must involved improving the overall management of peridomestic areas to prevent stable colonization.

Epidemiological risk for Trypanosoma cruzi transmission by species of Phyllosoma complex in the occidental part of Mexico.

Domestic and peridomestic triatomine populations were collected in three rural Mexican communities of Jalisco, Nayarit and Zacatecas states. Triatoma longipennis and T. picturata (Phyllosoma complex) were the principal species unequally distributed in the villages: T. longipennis was the main species in two communities and T. picturata in the third one. Peridomestic infestation and colonization indexes were remarkably high ranging from 26.1% to 50% and from 58.3% to 85.7%, respectively. Moreover, domestic (indoor) infestation was observed in only one of the communities infested by T. longipennis. The preliminary study of temporal variation indicates increasing trend of the triatomine population and infestation rates during the dry season. Triatomine infection rates ranged from 41.2% to 60.2% and all the flagellate isolates were assigned to T. cruzi I. The majority of the dwellings were built with modern building materials and the sanitary conditions were generally good. High peridomestic infestations must be considered as a risk factor of Chagas disease transmission and further studies are needed to better understand the peridomestic conditions favoring the establishment of the triatomines. The contribution of such study to enlarger knowledge of epidemiological features of Chagas disease in Mexico is considered.

Colonization of rock pile boundary walls in fields by sylvatic triatomines (Hemiptera: Reduviidae) in Jalisco State, Mexico.

Granite rocks is a very abundant material in Mexico because they are used habitually as borders for fields. The current work established the significance of this ecotype as a colonization site for triatomines of the Phyllosoma complex. Seven sites, arbitrary selected, in San Martin de Hidalgo municipality (Mexico) were investigated in April 2002 by using 210 mouse bait-traps left during the night in wall hollows. One hundred and seventy-two triatomines of all life stages were collected from the seven sites. Triatomines adhered to the tape that covered the traps or were found near them, and 36.6% of the traps collected triatomines. The principal species was Triatomia longipennis Usinger (1939) and low numbers of Triatoma picturata Usinger (1939) were found. The nymphal population was very young, probably corresponding to the reproductive period in April (end of the dry season). The infection rate of the triatomines for Trypanosoma cruzi was 49%. Because collecting triatomines in the field is laborious and time-consuming, the mouse bait-trap method found to be practical to assess the population of triatomines within a sylvatic habitat.

Preliminary results of random amplification of polymorphic DNA among Triatominae of the phyllosoma complex (Hemiptera, Reduviidae)

In Mexico, Triatoma longipennis (Usinger), Triatoma picturata (Usinger), and Triatoma pallidipennis (Stal), primary Chagas disease vector species of the phyllosoma complex, were analyzed by randomly amplified polymorphic DNA (RAPD). Sixteen decametric primers resolved individual profiles not identical, but partially discriminative between species. Analysis based on pairwise presence/absence comparisons between the three species was performed using three primers and two outgroup species Triatoma infestans (Klug) and Triatoma barberi (Usinger). Fifty-three bands in total were scored, although only two bands were constant among the three phyllosoma complex species. Two other bands were constant only for T. longipennis and T. picturata together, and not present in T. pallidipennis. Neighbor Joining tree and the multiple correspondence analysis discriminated T. pallidipennis clearly from the other two species, although there was overlap between T. longipennis and T. picturata. The results indicate a close relationship between the studied species and support the hypothesis of their recent evolution. The suitability of RAPD to discern populations within the species is discussed.

Preliminary results of random amplification of polymorphic DNA among Triatominae of the phyllosoma complex (Hemiptera, Reduviidae).

In Mexico, Triatoma longipennis (Usinger), Triatoma picturata (Usinger), and Triatoma pallidipennis (Stal), primary Chagas disease vector species of the phyllosoma complex, were analyzed by randomly amplified polymorphic DNA (RAPD). Sixteen decametric primers resolved individual profiles not identical, but partially discriminative between species. Analysis based on pairwise presence/absence comparisons between the three species was performed using three primers and two outgroup species Triatoma infestans (Klug) and Triatoma barberi (Usinger). Fifty-three bands in total were scored, although only two bands were constant among the three phyllosoma complex species. Two other bands were constant only for T. longipennis and T. picturata together, and not present in T. pallidipennis. Neighbor Joining tree and the multiple correspondence analysis discriminated T. pallidipennis clearly from the other two species, although there was overlap between T. longipennis and T. picturata. The results indicate a close relationship between the studied species and support the hypothesis of their recent evolution. The suitability of RAPD to discern populations within the species is discussed.

Isoenzyme clustering of Trypanosomatidae Colombian populations.

Thirty-six Trypanosomatidae stocks isolated from various hosts and geographical areas in Colombia and 7 others from Bolivia, Chile, Honduras and Panama have been surveyed by Multilocus Enzyme Electrophoresis (MLEE). Part of the Colombian stocks were previously characterized by morphology and biological behavior as belonging to Trypanosoma cruzi and Trypanosoma rangeli taxa, others were unknown species. The genetic variability observed at 13 different loci was considerable, since 38 zymodemes could be distinguished and 2 upper branches were observed. The first branch corresponded to T. cruzi and was divided in the two major phylogenetic subdivision of T. cruzi (T. cruzi I, T. cruzi II). The majority of the Colombian T. cruzi stocks (92%) felt into T. cruzi I. Only two stocks, isolated from sylvatic mammals, belonged to T. cruzi II. Among T. cruzi I, we did not observed any additional phylogenetic subdivision and host-dependent genotype specificity. The second branch was genetically very heterogeneous and included all T. rangeli stocks, the stocks isolated from bats and one stock isolated from a sylvatic R. prolixus vector. The stocks belonging to T. rangeli presented only one locus instead of two for the malic enzyme system. Since, the upper level of resolution of the isoenzyme method was exceeded, the current clustering study failed to draw a clear distinction between such a diverse set of Trypanosomatidae species.

Genetic variability and microdistribution of Triatoma infestans genotypes and Trypanosoma cruzi clones in Arequipa region (Peru)

Genetic varibility of Triatoma infestans and Trypanosoma cruzi populations was studied by isoenzyme analysis in two distinct areas of Arequipa province (Peru); one, Santa Rita de Siguas, being an endemic area for Chagas' disease, the second Arequipa, recently infected. Analysis of T. infestans genetic variability indicates, (i) temporal stability of genotypes found in Santa Rita de Siguas, (ii) high genetic differences between Arequipa and Santa Rita de Siguas populations suggesting minor contact between them, (iii) multiple origin of the T. infestans population in Arequipa, and (iv) poor dispersal capacity of T. infestans: the panmictic unit could be reduce to a house. Parasite isoenzyme analysis was performed in 29 Peruvian stocks of T. cruzi, mainly isolated from bugs taken in a single locality, Santa Rita de Siguas. The results show, (i) a high genetic polymorphism, (ii) nine different multilocus genotypes were detected and clustered in two different clades, (iii) most of the parasite isolates pertained to one of the clade and were genetically similar to those analyzed 12 years before. This sample allowed the study of the mating system of T. cruzi in strict sympatic conditions and gave more strength to the hypothesis of the clonal structure of T. cruzi populations.

Trypanosoma cruzi: expression of antigenic component 5 among 35 laboratory clones obtained from 18 different isozymic variants

Dois anticorpos monoclonais anticomponente 5 de Trypanosoma cruzi (I-35/115 e II-190/30) foram testados respectivamente em IFA e ELISA sobre 35 clones de T.cruzi isolados no laboratório. Entre estes 35 clones testados, 18 perfís isoenzimícos diferentes puderam ser detectados. Todos os clones foram reconhecidos exceto um clone que näo reagiu com o anticorpo monoclonal II-190/30. Estes resultados säo a favor da expressäo constante do componente 5 no meio do taxón T. cruzi

Specific humoral depression in chronic patients infected by Trypanosoma cruzi.

Realizamos um estudo comparativo entre o xenodiagnostico e os testes sorologicos para doenca de Chagas. Cento e cincoenta pacientes de algumas areas endemicas foram estudados. Quatro deles pareceram revelar um estado particular com um xenodiagnostico positivo e uma sorologia negativa, esta realizada com quatro diferentes tecnicas classicas (teste de inmunofluorescencia, ELISA: Enzyme Linked Immunosorbent Assay, teste de fixacao do complemento e teste de immuno-eletroforese). O soro de um dos pacientes que apresentou depressao humoral especifica mostra elevada quantidade de antigenos circulantes comprovada pela tecnica da immuno-eletroforese.Os autores sugerem o uso de um teste sorologico para detectar a presenca de antigenos circulantes de T. cruzi, alem da utilizacao de testes sorologicos classicos. Isto permitiria o diagnostico da doenca de Chagas em pacientes com uma baixa (ou mesmo inexistente) producao de anticorpos especificos